1. Field
Example embodiments relate to electronic devices, and more particularly, to electronic devices configured to reduce a contact resistance of a portion at which a metal and a semiconductor meet.
2. Description of the Related Art
When a metal is junctioned, adjoined or coupled to a semiconductor, such as silicon, a Schottky energy barrier is generated due to a work function difference between the two materials and a Fermi-level pinning phenomenon of the work function of the metal on the surface of the silicon. In this case, a contact resistance between the metal and the silicon increases, thereby resulting in an increase in an operating voltage and consumption as thermal energy, and thus it is difficult to use the metal-silicon junction. Therefore, in order to solve the generation of the Schottky energy barrier, for generally used metal oxide silicon field effect transistors (MOSFETs), a junction is formed by increasing doping density at a silicon side, and a metal is junctioned, adjoined or coupled to the silicon.
However, according to the principle of MOSFET, a device design for preventing a junction leakage current by forming a p-n junction diode form with a substrate having low doping density is preferred. In addition, when a device size decreases, doping portions of a source and a drain meet each other, thereby resulting in a short channel effect such that a channel is not normally formed and causing a decrease in a device characteristic.
As another method of reducing the contact resistance between a metal and a semiconductor, pinning is prevented by generating a thin oxide on an interface between the metal and the semiconductor. However, it is typically difficult to uniformly generate a thin oxide layer, and if the thickness of the thin oxide layer is thick to a certain level, a contact resistance increases.